1. Technical Field
The present invention relates to hinge devices in general, and particularly to a portable computer having a hinge device for coupling two chassis to each other so that the two chassis can be opened and closed.
2. Description of Related Art
Portable information equipment such as a cellular phone or a notebook personal computer (laptop PC) employs a configuration in which a display chassis is coupled to a main body chassis by using a hinge device so that the display chassis and the main body chassis can be opened or closed.
Some laptop PCs include a hinge device having a uniaxial structure that rotatably supports a shaft disposed at an upper end of a hinge block standing on a back end portion of a main body chassis and fixed to a back end portion of a display chassis. Other laptop PCs (convertible PCs) include a hinge device having a biaxial structure that rotatably supports a shaft disposed at an upper end of a hinge block and fixed to a back end portion of a display chassis and rotatably supports a shaft disposed at a lower end of the hinge block and fixed to a back end portion of a main body chassis, and this display chassis can be inverted to a 360-degree position.
To obtain stable opening/closing operability of the display chassis, for example, and enable stable holding of the display chassis in a desired angle position, the hinge device of the portable information equipment as described above needs to generate a sufficiently large rotational torque. In view of this, a hinge device of a related art portable information equipment employs a torque generation mechanism in which a rotary plate is provided coaxially with a rotation shaft fixed to a display chassis and a main body chassis and a stationary plate for generating a frictional force with the rotary plate is provided at a hinge block.
In the field of portable information equipment, the thickness of chassis has rapidly decreased. Thus, hinge devices each for coupling two chassis to each other are required of reduction in the thickness direction of the chassis. A biaxial structure has needed to conform with the reduced thickness of equipment by reducing the distance between two shafts.
On the other hand, to generate a desired rotational torque by the torque generation mechanism, a certain contact area needs to be obtained between the rotary plate and the stationary plate, and reduction of this contact area has a limitation. That is, there has been a problem that the torque generation mechanism is an obstacle to size reduction of the entire hinge device.
Consequently, it would be desirable to provide an improved hinge device that can reduce the size of a device configuration and can generate a desired rotational torque.